Production of hexamethylenetetramine and ammonium chloride



Dec. 22, 1925. 1,566,822

C. B. CARTER PRODUCTION 0F HEXAMETHYLENETETRAMINE AND AMMONIUM CHLORIDE Filed July 26, 1924 /Z- (f5 I Q jg 6 y? l l@ @j java/'2752; @arf/ej 6a?" @7j lza'ienterll Dec.` 22 1925.

' UNITED STATES 1,566,822 PATENT OFFICE.

CARNIE B. CARTER, OF PITTSBRG-H; PENNSYLVANIA, ASSIGNOR T0 S. KARPEN @c BROS., OF CHICAGO, ILLINOIS, A CORPORATION OF WEST VIRGINIA.

- PRODUCTION OF HEXAMETHYLENETETRAMINE AND AMMONIUM CHLORIDE'.

Application led July 26,

ITo all whom it may camera.'

Be it known that I, CARNIE B. CARTER, a citizen of the United States, residing at Pittsburgh, in the county of Allegheny and State of Pennsylvania, have invented a new and useful Improvement in the Production of Hexamethylenetetramine and Ammonium Chloride, of which the following is a specification. v

.This invention relates particularly to a method of producing hexamethylenetetramine and ammonium chloride.

The primary object is to provide a process for enabling hexamethylenetetramine to be produced in substantially pure form at very moderate cost. According to this method, the use of expensive solvents is avoided, and the necessity for evaporation of water is reduced to a minimum. Methylene chloride reacts with ammonia to form hexamethylenetetramine and ammonium chloride in accordance with the following equation:

The reaction may be carried out in practice, as has been pointed out in earlier applications, either in aqueous or liquid ammonia solution.

When the reaction is carried out in liquid ammonia the recovery of hexamethylenetetramine from the reaction product offers no particular difficulty;` it is a comparatively simple matter to separate the hexamethylenetetramine from the ammonium chloride by extraction with chloroform or other suitable solvent. Such solvents, however, are expensive and recovery accordingly is expensive.

When the reaction is carried out in aqueous ammonia solution the hexamethylenetetramine andl ammonium chloride are obtained in aqueous solution from which hexamethylcnetetramine and ammonium chloride cannot be obtained in a mechanically mixed form by simple evaporation of the water. The diliculty here lis that secondary reactions take place during the evaporation which result inv the loss of a part of the hexamethylenetetramine, as formaldehyde and ammonia and which also result in the formation of considerable amounts o hexaniethylenetetramine hydrochloride. The residual salt mixture recovered by such evaporation when extracted with chloroform 1924. serial- No. 728,464.,

or other suitable solvents does not yield the full theoretical amount of hexamethylenetetramine, and under some conditions may give only a small proportion of the theoretical yield. It is essential, therefore, that the evaporation of such solution shall be performed under such conditions that free ammonia shall be present in the solution and salt mixture at all times during the evaporation and drying. If these precautionary measures are taken complete recovery of hexamethylenetetramine from the residual salts may be made. In whatever manner the hexamethylenetetramine is produced, however, the problem of effecting separation in an inexpensive manner is important.

In my pending application No. 691,673, filed in the United States Patent Office, February 9, 1924, is described a process by which hexamethylenetetramine may be produced veryadvantageously by a reaction between methylene chloride and aqueous ammonia, the reaction being greatly facilitated by the use of a large excess of ammonia. However, it is now evident that, from a practical standpoint, one of the chief'diiculties to be overcome in the manufacture of hexamethylenetetramine from methylene chloride, using aqueous ammonia solutions, is that of recovering the hexamethylcnetetramine from the reaction liquor. In the present invention, advantage is taken of an increased solvent effect of aqueous solutions for ammonium chloride and a decreased solvent effect of such solutions for hexamethylenetetramine by introducing into, or surcharging, the solution with ammonia gas. The ammonia gas can be distilled of and recovered at small expense. By the improved method, it is possible to avoid the use @of expensive solvents and to lower the evaporating costs greatly.

The solvent power of water for hexamethylenetetramine is greatly reduced by saturating the solution with alnmonia. Hexamethylenetetramine is soluble to the extent of about 90 grams per 100 cc. of water, in the absence of ammonia, but the solvent power is reduced to 10 or 15% of this amount if the Water be surcharged with ammonia. It is possible to precipitate. as much as 90% of hexamethylenetetramine from a saturated solution by introducingr ammonia gas into the solution. In liquid ammonia, the hexamethylcnetetraniine concentration bepletely saturated with ammonia, the hexamethylenetetramine concentration `is very."`

low, indeed. v v

On the other hand, the introduction vof ammonia into .an aqueous solution of ammonium chloride greatly increases the solubility for ammonium chloride. Water dissolves about 39grams of ammonium chloride per 100 cc. at ordinary temperaturesl .and about 77 grams per 100 cc. at 90o C. The introduction of ammonia into the solu tion increases the solvent power of water with increasing ammonia concentration, and 100 cc. of vwater at ordinary temperatures carrying` 21.8 grams of ammonia per 100 cc. of solution will dissolve 63.5 grams of ammonium chloride. Liquid ammonia will dissolve still more ammonium chloride than will an aqueous solution saturated with `am monia, There 1s, of course, an expansion of the aqueous solution duriiig the introduction of ammonia, so that. the amount of either hexamethylenetetramine. 1or ammoniper 100 cc. of the solution itself is less" than when expressed in terms of the original' 100 The `'solvent power of aqueous ammonia solutions for hexamethylenetetramlne and ammonium chloride, `each, .1s not appreclably affected by the. presence vof both .these substances in the same solution. In the following table, the solubilities of .hexamethylenetetramine and `ammonium chloride in aqueous ammonia solutlonsare expressedfm grams of 100 cc. offsolutiomand also per.

100 cc. of water.

Solub'ihtes.

,l Per 100 cc. of'solution. Per 100 cc. of water.

Nm. Hexa- NH4C1. Nm.y nem. Nmcl. p y

0.0 41.5 20.2 0.0 90.5 38.6 a3' am 21.2 10.6 61.5 42.4 .a1 29.1 21.9 las 60.5 44.6 13.8 21.1 I 241 30.8 41.1 55.2 2&4 4.2v 222 16.0 11.2 @las It is very clear that there is a very marked 1 decrease'- in the solubility. ofhexamethyleney' tetramine with rising ammonia concentra'-y tion and, at the same time, a .marked in* crease in the solubility of ammonium chloride in the same'solution. In fact, the solubility of hexamethylenetetramine is reduced about 87.6%, and the solubility of ammonium chloride is of its formerV value. l

Saturation of the solutions shown in the foregoing experiments was carried. out 'at somewhat lowered temperatures. It is to be noted, however, that the same eects can be secured at higher temperatures if the 1 fsome increased to about 170% h under. pressure. e In my application No. 728,463 liled in the '1 ammonia .is'introduced into-the solution l nited -States Patent Office. on even date herewith, -it is pointed out how these phenomena can be employed in a practical 'Way inthe recovery of hexamethylenetetramine from mlxturescontalnmg ammonium chloride. Such mixtures may be composed of the dry salts obtainable, for example, by

producing hexamethylenetetramine by a reaction between liquid ammonia and methylene chlorlde, 1n which reaction ammonium mixture may be composed of th'eJwet salts, such as may be obtained from. a reaction between methylene chloride and aqueous amchloride is lformed as a by-product; or the l i monia, followed by evaporation of most of upon methylene. chloridewith ammonia iu f aqueous solution, the ammonia being prefum chloride which will be held in solution l'erably used in large excess above the theoretical amount required for the reaction.

Inl accordance with.the present process,

which maybe termed a stock liquor, is

charged into an autoclave, which also re- .ceives a Ycharge of methylene 'chloride and ammonia suiicient to combine with the methylene chloride and also to provide an excess of several hundredpercent abovethe .theoretical amount -necessary for the reac-- tion, such excess serving to facilitate and expedite the reaction`V and enable .the process 'to be carried out within a reasonably short p e'riod and at pressures which are not excesslve; the autoclave is heated at a suitable temperature, say .100 C., or less, untilthe reaction is complete; the liquor is then passed to a saturator and surcharged with ammonia. 5 "gas, the device being suitably cooled; the

'contents of the 'saturator composedy largely helxamethylle'netetramine, are passed to af of af solution of ammonium chloride and l.

hexamethylenetetraminey saturated L# with ammonia, and also of the precipitated" ilter, where the precipitated hexamethylenetetramine is separated from the liquor'.l

the liquor then being passed to a still an lthe hexamethylenetetramine being washedvand passed to a dryer;l the ammonia is distilled off and returnedv to thelammonia stor- 'age tank; the liquor is discharged into ay cooler and precipitator,jwhere much of theammonium chloride is precipitated; the ma' f terial is then passed to a filter where the "liquor is separated from the precipitated ammonium chloride; the ammonium ychloride is then washed on the filter, vand passed `to a dryer.; the .filtrate is passed to an evaporator Where a portion 'of the water (correstorage-tank from which the autoc ave draws its'supply. Thus, the ammonia 'employed in the process is reused, and the stock liquor is reused, ammonia being used in sufiicient anount in the process to suitably "increase the solvent power of the liquor for ammonium chloride and reduce the solvent power of hexamethylenetetramine, so that the hexamethylenet'etramine can be thrown out at one point in the system, the ammonia can be distilled and returned to the source of supply, and the liquorthus placed in condition to deposit, at aseparate point in the system, a large portion of the ammonium chloride, the .precipitation here obtained resulting both from the removal of the ammonia from the liquor and the cooling of the liquor.

The accompanying drawing illustrates, diagrammatically, -a, system and apparatus which may be advantageously employed in the practice of the process. The process fwill be further described with reference to said drawing.

A represents a storageftank for methylene chloride; B, an autoclave; C, a storage-tank for ammonia which may be llqp'id ammonia; D, a stock liquor storage-ta E, a cooler and saturator which receives the solution from the autoclave after the reaction between the methylene chloride andV ammonia has been effected, andv which receives also ammonia in large enough quantity to eiect precipitation of the bulk of the hexamethylenetetramine contained in the solution, the reduction in temperature adding also,in some degree, in effecting precipitation of hexamethylenetetramine; F, a storage tank for aqueous ammonia; G, ai filter and washer where the precipitated hexamethylenetetramine isseparated; from the liquor, the liquor passing then tb a still and the hexamethylenetetramine being washed on the filter,- the wash-water passing to an evaporator; H, a dryer for hexamethylenetetramine;

i 'I, a still which receives the motherdiquor from the device G, which device may be either an ordinary iilter or a centrifuging machine; "J, al storage chamber for hexamethylenetetramine; K, a cooler and precipitatorwhich receives the contents from Y' the still'I after Vthe ammonia has been distilled off, a large portion of the ammonium cipitated in the vessel K as a result of cooling the liquor; L, a filter and washer where Y the precipltated ammonium chloride is separated from the liquor, the uor being with-Y drawn to an evaporator an the precipitate blin subjected to' a washing operation on t e e; M, a tank containing wash-water. which .1s free from am-l monia; N, la dryer fr the ammonium chloride; O, a storage chamberV for the am# ter, whichma be an ordinary lter or. a centrifuging mac monium chloride; P, an evaporator which receives the liquor' from the filter L; Q, an evaporater which receives the Wash-waterv from the ilter G;' R, ai condenser for' am' monia employed inthe system; and S, a condenser .for ammonia employed in the system. A

Lines of communication, or routings, between the various vessels and'chambersare designated l to 27 inclusive, the course of l materials being indicated by ,the arrows. The lines 2, 5 and 6 leadin from J:he liquid ammonia tank C are prefera le equipped with reducing valves 2, a'and 6, respectively.

The storage-tank D may originally contain pure water, if desired. `However, when the process is' operating normally, it will contain water having in solution a consider able quantit of ammonium chloride and a comparative y smallamount of hexamethylenetet-ramine. In the practice of the process, stock liquor is passed from the tank D into the autoclave; and methylene choride and ammoniavare introduced into the autoclave, the ammonia being taken in sufiicient amount to combine with the methylene chloride andA form hexamethylenetetramine and ammonium chloride. To facilitate the re action, the ammonia is preferably used in excess to an extent of 300 to 400% of the theoretical proportions, and this will tend to effect precipitation of hexamethylenetetramine as it is formed in the autoclave, andwill, at the same time, tend to increase the solvent power of the liquor or ammonium chloride. After the reaction is complete, the contents of the autoclaveare 'discharged into the cooler and saturator E and the liquor is then surcharged with ammonia, or, in any event, the ammonia is used in sufficient amount to cause the precipitation of a large portion of the hexamethylenetetramine con. tained in solution and, at 4the Sametime, to

insure that all of the ammonium chloride shall be in solution. The contents of the device E-are then passed tothe iilter G, where thehexamethylenetetramine is se arate from the liquor and the liquor is disc iarged into 'the still I. The hexamethylenetetramine is washed on the filter with aqueous ammonia,

which tends to precipitate hexamethylenetet` ramine, the wash-water is passed to the evaporation Q, where the ammonia may be distilled ofi', and where, if any excess water is introduced into the system, it may be evaporated oil to maintain the proper balance. At the still I, the ammonia is distilled returned bythe'lines-9and'7 to the-I' ammonia storage-tank C, va condenser being interposed in the line 7 The remaining conL vtents of the sti1l`I`are evacuated into the cooler andprecipitator K. It will be noted thatprecipitation of a large'portion of the ammonium chloride will result from the expulsion 'of the ammonia-and the cooling of the liquor. l0

The contents'of the vessel K are then passed to the lter L where the precipitated ammonium chloride is separated and passed to the dryer N .j The iltrate and washwater from the lter L are passed to lthe evapora-tor?, where 'a' partial evaporation is effected (corresponding. with4 washwater used), and themother-liquor, composed ,of water containing a considerable amount of-ammonium chlorideand a small 'amount of hexamethylenetetramine in solution is returned to the ster-age-t'ank l). Pure water is employed for washing the ammoniportion vofthe ammonium chloride. eva orated from the' dryer N' passes to the f was -water tank M. 'v

um chloiide at the lter L, no ammonia being employedat this point for the reason that it is desired to precipitate a larg e 7proA ater - t will be noted `fromthe description given '4 that the 'separation of .hexamethylenetetramine-from ammonium chloride is effected without the necessity-of evaporation ofthe solution, followed by the use of an expensive solvent for`ex'tracting the ammonium chloride from the hexameth'ylenetet-ramine. In the present method, theammonia can be distilled from the 'liquor at a small expense, 'andthe evaporation' of water necessary cor- I responds merely .withthat required for dr Y for A clearness ofunderstanding only, and no ing the salts and evaporating the wa v water employed at the ilter L v y If the ammonium chloride produced is to be employed as asourcefor ammonia, the

Y operation of this luy-product may bev '4'5 omitted, and the product may be taken in recovery plant. Y

.wet condition, fdlrectly to the ammonia The foregoing' description has. been given unnecessary vlimitations should jbe' understood therefrom,J but 4the y as permissi- .'ble, in view of the prior art'.

'5 5 cure by Letters Patent, is:

` ing hexamethylenetetramine'and ammonlum 1. The process of producing and separat.

chloride'which comprises :-lleating methylene chloride and aqueous ammonia and employ-v ing lexcess ammonia tov lower the solvent power of the liquor forhexam'ethyletetramine and increas'ethe same for ammonium chloride, separating theprecipitated hexamethylenetetraiiiine from the liquor, and distilling'ammonia fromthe liquor and cooling the liquor and thus precipitating ammonium ammonium chlori Y the resultant solution stronglymoniaand thus of the hexamet appended. claims* should be construed as broa chloride and se arating the precipitated am` I tetramine from the liquor, distillingfoii' the ammonia to lower the solvent power of the liquor forv ammonium chloride, cooling the remaining liquor, ,and separating the'precipitated ammonium chloride from the liquor.

3. The process which -comprises'zicausing a reaction between methylene chloride and ammomain an aqueous solvent contamlng ammonium Achloride andi hexamethylenetet-- raminein solution, the -ammonia being einployedin the solution in greater than' the 'theoretical proportion, treating the solution with ladditional ammonia to lower the solvent A power for hexamethylenetetramine and-cause precipitation 'of hexamethylenetetramine, v

.separating the preci itated hexamethyleneammonia -for reuse,

the ammonium chloride,` separating the' precipitated ammonium chlorlde from the liquor, andv in the solvent.

tetraminef/from the iquor, distilling off'the ammoniavfrom the liquor and returningthe cooling the remaming liquor and 'preci-pitatg a largeportion of,

10o' returning the liquor for reuse. f

4. The process luuhichl comprises :l heating tetram'ine,

bine withthe meth lene, chloride,

the liquor to lower ,the solvent? power for ammonium chloride, cooling the liquor, and

ride'from the'. liquor.

' 5.v The process which comprises: heating. methylene chlorlde and an aqueous solution -12`0- of ammonium` chloride and hexamethylene- @methylene chloride and an aqueoussolution of ammonium chloride and hexamethylene--` l chargedwith'ammonia in excessf of thel theoretical amount requiredfto cornf charging with 'amli recipitating' a large portion, .UU 'L' ylenetetramine, separating-` the, precipitated, hexamethylenetetramine fromthe liquor, distilling ammoniaI from f tetramine, charged vwith ammonia in' excess f of the theoretical amount Jrequired to combine withffthemethylene chloride, charging the resultant solution strongly with amrecipitating a large portion monia and thus of the -hexamet lenetetramine, separating the preclpitate hexamethylenetetramine from the liquor, distilling ammonia from the liquor, returning the ammonia to the source of supply, cooling the liquor, separat- 1'1'82.' separating the precipitated ammoniumv chloe methylenec 1 1o ing' the. from the quor, `and em loying the liquor as a stock lsolution in wllxich to Vcarry out the reaction between methylene chloride and ammonia.

y 6.' The continuous process of hena- "methyl'elnetetramine and ammonium-jc oridev which compis'es: lheating `in an autoclave monium chloride in solution, in the presence of ammonia.l employed in greater-than theoretical proportion, coolin vthe' liquor agiter the rectionjand s'ubstentially saturat# f precipitated ammonium clilorideV` oride and water containing am Y I chloride, 'and returningr't and Ydistilling oft' the ammonia. to lower the solvent power`of the liquor for ammonium chloride, vcooling the contents of the still, separting the precipitated ammonium chloride' onfa -lterand washin the ammonium e solvent to 'a sou'rce ofl supply.

- cARNmn CARTER. o 

